help programming ATtiny 4313 for led 5x7 matrix

I was hoping someone could help me in decoding this code so that I may modify it to scroll text and add new images.
I'm a noob when it comes to the arduino and microcontrollers so any help would be appreciated.
I have been google ing for two days with no results
I'm going to start reading C++ tutorial today and maybe that will help.
Thank you everyone for any help you can provide

I have attached the code I would like to edit.

TinyMatrix.c (10.2 KB)